Milk powders, such as skimmed milk powder and buttermilk powder, are used in a wide variety of foodstuffs including confectionery, infant formulas, bakery products, dry mixes (e.g. pancake or biscuit mixes, beverage mixes), soups, fermented milk products, ice cream and frozen dairy desserts, processed cheese, and meat products. Further, skimmed milk powder is often used in reconstituted (with water) or recombined (with water and fat) form, especially in places or circumstances where storage of fresh milk is difficult.
Two major constituents of milk powders are milk proteins and reducing sugars, primarily lactose. When milk proteins are heated in the presence of reducing sugars, free amino groups of the proteins will react with the sugars resulting in glycation of the proteins. If such reactions are allowed to proceed unchecked, the result can be a substantial reduction in nutritional value and some browning may also be observed. The complex series of reactions that can occur are known collectively as the Maillard reaction. Indeed, it is even thought that Maillard type reactions may occur, albeit very slowly, in food products containing the necessary chemical groups at room temperature. Although the Maillard reaction is generally thought of as undesirable and steps are therefore taken to control it during processing of the relevant foodstuffs, more recently it has been realized that carefully controlled glycation of milk proteins might offer the opportunity to manipulate the properties of the proteins in various ways.
The first irreversible product resulting from the non-enzymatic interaction of a glycosyl group and the α- or ε-amino groups of proteins is known as an Amadori compound. All Amadori compounds generate furosine when subjected to acid hydrolysis and accordingly a method of monitoring the progress of glycation of milk proteins based on measurement of furosine production was devised. With this tool and the subsequent development of mass spectrometry techniques, it became theoretically possible to monitor the progress of the Maillard reaction. Glycation can be carried out in solution or in the solid state. However, according to Morgan et al. (Modification of bovine beta-lactoglobulin by glycation in a powdered state or in an aqueous solution: immunochemical characterization, J Agric Food Chem (1999) 47, 4543-8), solid-state processes result in less conformational change of the protein molecule. Further, solid-state processes are easier to monitor and control.
International application WO 00/18249 describes a process for the solid-state glycation of powdered whey protein-containing materials comprising adjusting the water activity of the powder to 0.3 to 0.8 and allowing glycation to proceed at a temperature of 30 to 75° C. for between 1 hour and 80 days. It is claimed that the resulting powder has enhanced functional properties, such as enhanced heat stability, emulsifying activity, antioxidant activity and enterotoxin binding capacity.
Given the wide range of uses of milk powders described above, it can be seen that powders having different properties may be more effective for certain uses than others.
U.S. Pat. No. 6,548,099 relates to a process for crystallizing amorphous lactose in milk powder for preparing chocolate products. The process includes (a) contacting milk powder with water in an amount sufficient to initiate crystallization and (b) treating powder to heat and shear forces at a temperature above the wetted milk powder. The combination of shear and heat helps liberate the entrapped fat and therefore improves the rheological properties of milk, improves the texture and mouthfeel in the production of chocolate.
US published patent application 2004/0208967 relates to a method and system for converting liquid products into free-flowing powders with pre-cooling. The method includes the heating of the liquid product to a temperature above the crystallization of any component in the liquid product in a heat exchanger, subsequently flash separating volatile components from the heated liquid to obtain a paste concentrate, then, precooling a fraction of the paste concentrate and drying the combination of precooled and non-precooled concentrate.
An example of a common use of milk powders is as a constituent of dry beverage mixes which are delivered through vending machines. These beverages may be served hot or cold, and include coffee, tea, chocolate, soup and the like. For this purpose, it is desired that milk powders possess specific physical properties to avoid such problems as caking of the powder. For example, good flow properties allow for accurate dosing of the powder which results in an optimum taste in the resulting beverage and minimized powder wastage. Further, powders with improved solubility allow beverages to be dispensed more rapidly and the resulting beverages contain less undissolved powder.
With the increasing demand for cold beverages, the solubility of milk powders at low temperatures is also an issue. This is an obstacle to producing cold beverages from a beverage distribution machine. Solubility of milk powder can be improved by the addition of additives such as salts, wetting or surface-active agents. However, these agents are not always sufficiently effective and desirable. Therefore, there is a need for a milk powder that dissolves better and faster in cold water with less or even preferentially no additives.
One of the objectives of the present invention is to provide a modified milk powder having improved flow properties and/or improved solubility in cold water.